Salt recovery or precipitation is used in various industries to recover a desirable or usable naturally occurring salt product suspended or dissolved in a fluid. For example, potassium chloride, or potash, is a salt that is naturally occurring and usable in a variety of applications such as for fertilizer, food, and pharmaceuticals. Potash is generally produced through two methods, conventional mining techniques and solution mining depending upon deposit depth and geology. Solution mining is often used in situations where the deposits are too deep or too thin for conventional mining techniques, and solution mining generally creates minimal surface disturbance and little waste compared to conventional mining. Other advantages of solution mining include the fact that impurities can be readily removed allowing for the production of high-grade salt for other uses, including food, chemical, and pharmaceutical manufacturing. Additionally, any impurities (i.e., insolubles) are readily disposed of by reinjecting them into a solution mining cavern.
In solution mining, heated fluid, for example, heated water or a heated, salt saturated brine, is pumped into a cavern holding deposits of potash or potassium containing salts including sylvite (i.e., potassium chloride), halite (i.e., sodium chloride), and sodium sulfate. Due to the high dissolvability of these salts, the salts are dissolved into the heated fluid while leaving other salts behind. The heated fluid, now including the potassium containing salts, is then pumped to the surface for recovery and further processing.
Many solution mining operations utilize solar based evaporative ponds to evaporate water for recovery of the potassium containing salts. In some locations, reduced ambient temperatures associated with a mine location offers the ability to cool the fluid based on convective cooling between the fluid and ambient air. As the fluid cools, the saturation limits of the salts are reached and the salts begin to precipitate. As the salts precipitate out of solution, they settle to the bottom of the cooling pond where floating surface dredges can be used to scoop and remove the precipitates from the cooling ponds. The potassium containing salts can then be directed to a processing facility, where they can be processed for transport and sale.
As the thermal characteristics of the cooling ponds have a direct impact on the amount of salts precipitated from solution, it would be advantageous to improve the cooling performance of existing cooling pond systems without requiring substantial investment or process interruption.